Customers of high-quality printing systems and services demand the ability to reproduce their desired input images with accurate output (e.g., accurate color rendition) that does not significantly vary over time, among various rendering devices, or even spatially within the page. These considerations are more difficult to achieve with color rendering devices because of various image quality factors related to the state of the device, and more particularly, the print engine. Due to spatial non-uniformity errors, pixels with same color (CMYK mixture) printed in one part of an image may very well appear different when the same CMYK color mixture is used at another part of the printed page. The imaging, development and/or transfer subsystems of a print engine (including charging, development system wire history and wire contamination, charging subsystem variations and photoreceptor variations) are among many of the root causes for spatial non-uniformity errors in images. When memory colors those having a predefined color intent—for example “Xerox red” or “IBM blue”) with a desired CMYK mixture are printed, we may get non-uniformity errors in the image, if the same memory color is rendered as multiple pixels side by side covering a reasonably large area in the page. Customers may wish to achieve consistency and predictability of those specific marked colors within the page as well as across pages and even across printers. Consistency with respect to time, accuracy to the desired input, and uniformity in the imaging of such colors enhance the distinguishing nature of memory colors and protect and maintain its integrity and value to more sophisticated customers.
In one embodiment, memory colors would be a new customer feature to select or specify on printers. Reference is made to the following patent and publications, which illustrate methods and systems for achieving consistency over time and across printers for in-gamut and out-of-gamut colors without addressing uniformity:
U.S. Pat. No. 6,744,531 to Mestha et al. for a COLOR ADJUSTMENT APPARATUS AND METHOD;
US Publication 20020093684 by Bares et al. for ACCURATE PRINTING OF PROPRIETARY MARK PATTERNS AND COLORS, filed Dec. 6, 2000; and
US Publication 20050030560 by Maltz et al. for METHODS AND SYSTEMS FOR CONTROLLING OUT-OF-GAMUT MEMORY AND INDEX COLORS, filed Aug. 5, 2003.
Although methods have been proposed to obviate xerographic defects for single separation images, when colors are mixed, the defects are still visible and cannot consistently be overcome by those systems. US Patent Publications 20040252905, by Mizes et al. for SYSTEMS AND METHODS FOR COMPENSATING FOR PRINT DEFECTS, and 20050099446, by Mizes et al. for SYSTEMS AND METHODS FOR COMPENSATING FOR STREAKS IN IMAGES, are examples of such methods. More specifically, such systems do not show how to construct spatial inverse maps for memory colors, although an instance of such maps for memory colors at a macro level, over time, is believed to be understood.
In view of the noted problems, the present disclosure is directed to a method to render spatially uniform memory colors when images printed with CMYK primaries are not rendered uniformly due to print quality errors. The disclosed method uses an array of sensor to scan a test image across a process direction. Colors of interest are printed at the desired location first and then adjusted (iterated once or twice) to achieve the desired output quality. Iterations are carried out on the image on desired memory colors at the spatial resolution available in the measurement system. Colors of pixels are modified based on position where the pixels will be rendered, thereby compensating for any position/process related differences. Also disclosed in detail below is a process for incorporating modified memory colors before rendering, and the extension of memory color concepts to adjust colors for the uniform blocks (not edges), with uniformity defined by user definable thresholds. The effectiveness of the disclosed method was demonstrated via simulation for selected memory colors using computer models for prints from a Xerox iGen3 output engine.
Disclosed in embodiments herein is a method for dynamically generating a uniform color object in a printing system, comprising: identifying at least one memory color object from an image; using the image as an input, printing a test image; scanning the test image to produce scanned image data; extracting the memory color object from the scanned image data; and using the at least one memory color object and the scanned image data, generating an inverse spatial color map.
Also disclosed in embodiments herein is a method for consistent color generation on an image output device, comprising: identifying at least one memory color object from an image; using the image as an input, outputting a test image; scanning the test image to produce scanned image data; extracting the memory color object from the scanned image data; and using the at least one memory color object and the scanned image data, generating an inverse spatial color map for the output device.
Disclosed in embodiments herein is a system for consistent color generation, comprising: a source of image data, said data including at least one memory color object; a printer, responsive to the image data, for printing the at least one memory color object and producing an output print; a scanner for scanning the output print, said scanner producing an output including a plurality of color values generated from scanning the at least one memory color object; and a processor for receiving the color values and from said image data and said color values generating an inverse color map.
The following disclosure will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment(s) described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the disclosure and as defined by the appended claims.